Roofing products, photovoltaic roofing elements and systems using them

ABSTRACT

The present invention relates generally to roofing products. The present invention relates more particularly to roofing products for use with photovoltaic elements, and to photovoltaic systems that include one or more photovoltaic elements joined to a roofing substrate. In one embodiment, a roofing product includes a flexible roofing substrate having a top surface, the top surface having one or more granule-coated zones thereon capable of acting as a receptor zone or an exposure zone, each zone being adapted to receive one or more photovoltaic elements; and an adhesive suitable for securing photovoltaic elements to one or more of the granule-coated zones, the adhesive capable of forming a bond to the granules and the top surface of the flexible roofing substrate and to the bottom surface of the photovoltaic elements.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/853,972, filed Aug. 10, 2010, which claims priority under 35U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No.61/232,739, each of which is hereby incorporated herein by reference inits entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to roofing products. The presentinvention relates more particularly to roofing products for use withphotovoltaic elements, and to photovoltaic systems that include one ormore photovoltaic elements joined to a roofing substrate.

2. Technical Background

The search for alternative sources of energy has been motivated by atleast two factors. First, fossil fuels have become increasinglyexpensive due to increasing scarcity and unrest in areas rich inpetroleum deposits. Second, there exists overwhelming concern about theeffects of the combustion of fossil fuels on the environment due tofactors such as air pollution (from NO_(R), hydrocarbons and ozone) andglobal warming (from CO₂). Moreover, the very discovery and exploitationof fossil fuels carries significant environmental risk. In recent years,research and development attention has focused on harvesting energy fromnatural environmental sources such as wind, flowing water, and the sun.Of the three, the sun appears to be the most widely useful energy sourceacross the continental United States; most locales get enough sunshineto make solar energy feasible.

Accordingly, there are now available components that convert lightenergy into electrical energy. Such “photovoltaic cells” are often madefrom semiconductor-type materials such as doped silicon in either singlecrystalline, polycrystalline, or amorphous form. The use of photovoltaiccells on roofs is becoming increasingly common, especially as deviceperformance has improved. They can be used to provide at least asignificant fraction of the electrical energy needed for a building'soverall function; or they can be used to power one or more particulardevices, such as exterior lighting systems.

Photovoltaic cells can be packaged as photovoltaic elements, in whichone or more photovoltaic cells are electrically interconnected andprovided in a common package. One common type of photovoltaic element isan encapsulated photovoltaic element, in which the photovoltaic cellsare packaged together in between layers of layer material. The layermaterials are often chosen to be highly light-transmissive, and toretain their transmissivity over time. Encapsulated photovoltaicelements can be convenient for integration with various substrates.

Roofing products in which a photovoltaic element is integrated with aroofing substrate (such as a shingle or tile) have been proposed. Such“photovoltaic roofing elements” (also known as “roofing-integratedphotovoltaics” or “RIPV”) can provide both protection from weather andpower generation capability in a single product. Moreover, photovoltaicroofing elements can provide aesthetic benefit, as they can be made toblend with the architecture of the overall roof much better than canconventional photovoltaic modules.

Encapsulated photovoltaic elements can be convenient for integrationwith various substrates. However, in many circumstances, formation of along-lived physical connection between the material of the encapsulatedphotovoltaic element and the material of a substrate can be difficult,especially when the materials used to make the encapsulated photovoltaicelement have low surface tension. Notably, the surfaces used as the toplayer of many roofing substrates, such as the coated granules typicallyused with bituminous roofing products, can be less than optimal foradhesion to a photovoltaic element.

There remains a need for roofing products and photovoltaic roofingsystems that can address these deficiencies.

SUMMARY OF THE INVENTION

One aspect of the present invention is a roofing product for use withone or more photovoltaic elements, the roofing product including:

-   -   a flexible roofing substrate having a top surface, the top        surface having one or more granule-coated zones thereon capable        of acting as a receptor zone or an exposure zone, each zone        being adapted to receive one or more photovoltaic elements; and    -   an adhesive suitable for securing photovoltaic elements to one        or more of the granule-coated zones, the adhesive capable of        forming a bond to the granules and the top surface of the        flexible roofing substrate and to the bottom surface of the        photovoltaic elements.

A photovoltaic roofing element including:

-   -   the roofing product as described herein, with the adhesive        disposed in the granule-coated zones; and    -   one or more photovoltaic elements disposed on the adhesive in        the one or more granule-coated zones of the top surface of the        flexible roofing substrate.        In certain embodiments, at least some of the granule-coated        zones remain exposed as exposure zones.

Another aspect of the present invention is a photovoltaic roofingelement including:

-   -   a flexible roofing substrate having a top surface, the top        surface having one or more granule-coated zones thereon capable        of acting as a receptor zone or an exposure zone;    -   an adhesive covering and filling at least a portion of the        granule-coated zones; and one or more photovoltaic elements        disposed on the adhesive in the one or more granule-coated zones        of the top surface of the flexible roofing substrate,    -   at least some of the granule-coated zones remaining exposed as        exposure zones.

Another aspect of the present invention is a photovoltaic roofing systemincluding one or more photovoltaic roofing elements as described above,disposed on a roof deck.

Another aspect of the present invention is a photovoltaic roofing systemkit including:

-   -   a flexible roofing substrate having a top surface, the top        surface having one or more granule-coated zones thereon capable        of acting as a receptor zone or an exposure zone, each zone        being adapted to receive one or more photovoltaic elements;    -   an adhesive suitable for securing photovoltaic elements to one        or more of the granule-coated zones, the adhesive capable of        forming a bond to the granules and the top surface of the        flexible roofing substrate and to the bottom surface of the        photovoltaic elements; and    -   one or more photovoltaic elements suitable for disposition on        the adhesive when the adhesive is disposed in one or more of the        granule-coated zones on the top surface of the flexible roofing        substrate.

Another aspect of the present invention is a method for installing aphotovoltaic roofing system on a roof deck, the roof deck havingdisposed thereon at least one flexible roofing substrate having a topsurface, the top surface having one or more granule-coated zones thereoncapable of acting as a receptor zone or an exposure zone, each zonebeing adapted to receive one or more photovoltaic elements, the methodincluding:

-   -   disposing on a portion of the granule-coated zones an adhesive        suitable for securing photovoltaic elements to one or more of        the granule-coated zones, the adhesive capable of forming a bond        to the granules and the top surface of the flexible roofing        substrate; then    -   disposing one or more photovoltaic elements on the one or more        granule-coated zones of the top surface of the flexible roofing        substrate on which are disposed the adhesive.

Another aspect of the present invention is a method for installing aphotovoltaic roofing system as described above, the method including:

-   -   installing on a roof deck a flexible roofing substrate having a        top surface, the top surface having one or more granule-coated        zones thereon capable of acting as a receptor zone or an        exposure zone, each zone being adapted to receive one or more        photovoltaic elements; then    -   disposing on a portion of the granule-coated zones an adhesive        suitable for securing photovoltaic elements to one or more of        the granule-coated zones, the adhesive capable of forming a bond        to the granules and the top surface of the flexible roofing        substrate; then    -   disposing one or more photovoltaic elements on the one or more        granule-coated zones of the top surface of the flexible roofing        substrate on which are disposed the adhesive.

Another aspect of the present invention is a method for installing aphotovoltaic roofing system as described above, the method including:

-   -   disposing on a portion of the granule-coated zones of a flexible        roofing substrate having a top surface, the top surface having        one or more granule-coated zones thereon capable of acting as a        receptor zone or an exposure zone, each zone being adapted to        receive one or more photovoltaic elements an adhesive suitable        for securing photovoltaic elements to one or more of the        granule-coated zones, the adhesive capable of forming a bond to        the granules and the top surface of the flexible roofing        substrate; then    -   installing on a roof deck the flexible roofing substrate having        the adhesive disposed thereon; then    -   disposing one or more photovoltaic elements on the one or more        granule-coated zones of the top surface of the flexible roofing        substrate on which are disposed the adhesive.

Another aspect of the present invention is a method for installing aphotovoltaic roofing system as described above, the method including:

-   -   installing on the roof deck a flexible roofing substrate having        a top surface, the top surface having one or more granule-coated        zones thereon capable of acting as a receptor zone or an        exposure zone, each zone being adapted to receive one or more        photovoltaic elements an adhesive suitable for securing        photovoltaic elements to one or more of the granule-coated        zones;    -   providing a photovoltaic element having an adhesive on its        bottom surface; and    -   disposing the adhesive on at least a portion of the        granule-coated zones, thereby adhering the photovoltaic element        to the flexible roofing substrate.

The products, elements, systems, methods and kits of the presentinvention can result in a number of advantages. For example, in someembodiments, the products and systems of the present invention canprovide enhanced adhesion between a photovoltaic element and theflexible roofing substrate. In other examples, the methods of thepresent invention can be used to install a photovoltaic roofing systemso that the installation of the relatively rugged flexible roofingsubstrate can be performed by a roofing professional, and the morefragile photovoltaic elements can be installed much later, by a personskilled in electrical interconnections. Other advantages will beapparent to the person of skill in the art.

The accompanying drawings are not necessarily to scale, and sizes ofvarious elements can be distorted for clarity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic top view of a roofing product according to oneembodiment of the invention;

FIG. 2 is a schematic cross-sectional view of two embodiments offlexible roofing substrates;

FIG. 3 is a schematic top view and a schematic cross-sectional view ofroofing products with photovoltaic elements adhered thereto, accordingto one embodiment of the invention;

FIG. 4. is a schematic cross-sectional view of roofing products withphotovoltaic elements adhered thereto, according to one embodiment ofthe invention;

FIG. 5 is a schematic top view of a flexible roofing substrate accordingto one embodiment of the invention;

FIG. 6 is a partial schematic cross-sectional view of a flexible roofingsubstrate according to another embodiment of the invention;

FIG. 7 is a schematic cross-sectional view of a flexible roofingsubstrate according to another embodiment of the invention;

FIG. 8 is a schematic cross-sectional view of a roofing productaccording to one embodiment of the invention;

FIG. 9 is a set of top schematic views of flexible roofing substratesaccording to various embodiments of the invention;

FIG. 10 is a top schematic view of a flexible roofing substrateaccording to one embodiment of the invention;

FIG. 11 is an exploded schematic perspective view of an encapsulatedphotovoltaic roofing element for use in the present invention;

FIG. 12 is a schematic top view, and FIG. 13 is a schematiccross-sectional view of a photovoltaic element according to oneembodiment of the invention;

FIG. 14 is schematic top view of a photovoltaic element according to oneembodiment of the invention;

FIG. 15 is a top schematic view of a photovoltaic roofing elementaccording to one embodiment of the invention;

FIG. 16 is a top schematic view of a photovoltaic roofing elementaccording to one embodiment of the invention;

FIG. 17 is a top schematic view of a photovoltaic roofing elementaccording to one embodiment of the invention;

FIG. 18 is a top schematic view of a photovoltaic roofing elementaccording to another embodiment of the invention;

FIG. 19 is a top schematic view and a schematic cross-sectional view ofa photovoltaic roofing element according to another embodiment of theinvention;

FIG. 20 is a top schematic view of a flexible roofing substrate and aphotovoltaic roofing element according to another embodiment of theinvention;

FIG. 21 is a top schematic view of a photovoltaic roofing systemaccording to one embodiment of the invention;

FIG. 22 is a top schematic view of a photovoltaic roofing systemaccording to another embodiment of the invention;

FIG. 23 is a schematic perspective view of a photovoltaic roofing systemaccording to another embodiment of the invention;

FIG. 24 is a top cross-sectional view of a photovoltaic roofing systemaccording to another embodiment of the invention; and

FIGS. 25-28 are schematic perspective views of flexible roofing elementsand photovoltaic roofing elements according to one embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a variety of products, elements, systems,methods and kits for use in outfitting a roof with a photovoltaicsystem. According to one aspect of the invention, a flexible roofingsubstrate with a granule covering is provided. A photovoltaic elementcan be adhered to the granule-coated area of the roofing substrate usingan adhesive. For example, in certain embodiments, a locally flowablereactive adhesive is applied on the granule-coated area of the flexibleroofing substrate after it is installed on the roof. The adhesive flowsover the granules and into the crevices therebetween, thereby forminggood contact and strong bonding to the flexible roofing substrate. Aphotovoltaic element is disposed on the adhesive (i.e., so that itsbottom surface contacts the adhesive), and the adhesive can set or cureto lastingly adhere the photovoltaic element to the flexible roofingsubstrate. Notably, the adhesive can be applied in any desired geometry,such that any size or shape of photovoltaic element can be adhered tothe roofing substrate. A single photovoltaic element can be installedacross multiple roofing substrates, and multiple photovoltaic elementscan be installed on a single roofing substrate, depending on therelative sizes and shapes thereof. The adhesive can be selected suchthat it is flowable enough to penetrate in between the granules, yethave a shear resistance such that on a sloped roof, it remains in placewithout slumping due to gravity before the photovoltaic element isdisposed thereon. A variety of additional and alternative aspects andembodiments of the invention are described herein, for example, usingdifferent adhesive systems, roofing substrates, photovoltaic elementsand installation methods.

One aspect of the invention is a roofing product for use with one ormore photovoltaic elements. One embodiment of such a roofing productaccording to the present invention is shown in schematic top view inFIG. 1. Roofing product 100 comprises a flexible roofing substrate 110having a top surface, which has one or more granule-coated zones 114thereon (in this case, one). The granule-coated zones are coated withroofing granules. Notably, as described in more detail herein, agranule-coated zone is capable of acting as a receptor zone (i.e., forthe application and adhesion of one or more photovoltaic elements) or anexposure zone (i.e., to remain exposed and visible after one or morephotovoltaic elements are applied to the flexible roofing substrate,and/or after one or more overlying flexible roofing substrates areapplied). In use, the person of skill in the art can adhere one or morephotovoltaic elements to the granule-coated zones. Any areas of thegranule-coated zones not covered by photovoltaic elements (i.e., exposedareas), however, can have a desirable appearance as a result of thegranule covering the surface of the roofing substrate. Moreover, thegranules can protect the underlying materials of the roofing substratefrom UV-induced damage.

The sizes and shapes of the one or more granule-coated zones can, forexample, be selected based on the sizes and shapes of the photovoltaicelements envisioned for use therewith. For example, certain photovoltaicelements available from United Solar Ovonic have dimensions of about 12cm×18 cm (T-Cells); about 24 cm×36 cm (L-Cells); or about 40 cm×5 m(strip). Of course, in certain embodiments, the granule-coated zones arelarger in at least one dimension than the photovoltaic elements. In suchembodiments, when the photovoltaic elements are installed, any exposedarea is covered with granules, and therefore can have a desirableappearance and durability. In some embodiments, the granule-coated zonehas a dimension that is only somewhat larger than (e.g., in the range of101-120% of, or even 101-110% of) the corresponding dimension of thephotovoltaic elements with which they are to be used. Such embodimentscan be more user-friendly, as precise alignment is not necessary for aninstaller to accurately place the photovoltaic element completely withinthe granule-coated zone. In certain embodiments, when an elongatedphotovoltaic element is used, such as the strips available from UnitedSolar Ovonic, minor angular misalignments can be tolerated.

The flexible roofing substrate can be, for example, a bituminoussubstrate. For example, in certain embodiments it can be a bituminousroofing membrane. In other embodiments, the flexible roofing substrateis an asphalt shingle.

For example, in the embodiment of FIG. 1 the flexible roofing substrate100 is a conventionally-shaped and -sized laminated asphalt shingle. Theshingle has a granule-coated zone 114 and a headlap zone 118; in thisembodiment, the granule-coated zone 114 covers the entire area of theshingle that is not to be covered by overlying courses of shingles wheninstalled. In the headlap zone is a fastening zone 119, as isconventional in roofing shingles. In certain embodiments (e.g., asdescribed below with respect to FIG. 5), the shingle has a plurality oftabs formed in the area of the shingle that is not to be covered byoverlying courses of shingles when installed, as is conventional in theroofing arts.

The roofing product further includes an adhesive suitable for securingthe photovoltaic elements to one or more of the granule-coated zones.The adhesive is capable of forming a bond to the granules and the topsurface of the flexible roofing substrate and to the bottom surface ofthe photovoltaic elements. In certain embodiments, the adhesive isprovided disposed on the roofing substrate in the granule-coated zonebefore it is installed on the roof, for example, as described below, andas shown in FIG. 1 at reference number 140. In use, the roofing productcan be installed on the roof, then the adhesive used to adhere aphotovoltaic element thereto. In other embodiments, the adhesive isprovided separately, together with the roofing substrate in the form ofa kit. In such embodiments, the roofing substrate can be installed onthe roof, then the adhesive applied, for example, as described below.Moreover, in certain embodiments, the adhesive is provided as part of aphotovoltaic element having the adhesive on its bottom surface (e.g.,with a releasable liner in a “peel-and-stick” fashion).

In certain embodiments, the top surface of the flexible roofingsubstrate in the granule-coated zone is recessed from the top surface ofthe flexible roofing substrate in the area adjacent to thegranule-coated zone. For example, the shingle 200 a shown in schematicside cross-sectional view in FIG. 2, has a granule-coated zone 214 a anda headlap zone 218 a. The shingle 200 a includes a shim 220 a on its topsurface in the headlap zone. Fastening zone 219 a extends along theheadlap zone near its down-roof end. In another embodiment, the shingleis formed from overlapping materials, as shown in FIG. 2 with referenceto shingle 200 b. Shingle 200 b has a granule-coated zone 214 b and aheadlap zone 218 b. The shingle 200 b is formed from two overlappingsheets 220 b and 222 b of asphalt roofing material. The fastening zone219 b extends along the overlap area. Use of overlapping sheets inconstructing a shingle can, for example, allow the flexible roofingelement to lay flat on a roof deck.

In certain embodiments, the shim provides sufficient thickness so thatif a photovoltaic element is installed in the granule-coated zone, thetop surface plane of the photovoltaic element will be at or below thelevel of the top surface plane of an overlying course of shingles (asmeasured along the surface normal to the roof deck). Such an arrangementcan help aid in effective drainage and runoff of water from the roof.For example, FIG. 3 is a schematic top view and schematic sidecross-sectional view of two courses of roofing products as describedherein, with photovoltaic elements adhered thereto. Shingles 300 a(shown in dotted line, and only partially in the side view) are disposedon a roof deck (not shown) so that they overlie shingles 300 b. Shingles300 b have disposed in their granule-coated zones 314 b photovoltaicelements 330 b, adhered thereto with the adhesive 340 b. The shims 320 bare of sufficient thickness so that the top surface plane 311 a of theshingles 300 a is at or above the top surface plane 332 b of thephotovoltaic elements 330 b. As the person of skill in the art willappreciate, a shim can alternatively or additionally be provided on thebottom face of the shingle in its headlap zone to add thickness to theheadlap zone. The person of skill in the art will take into account therelative sizes of the headlap zone and the portion of the roofingsubstrate to remain uncovered by overlying elements in determining thesize of the shim.

The embodiment of FIG. 3 also includes a sealant 309 on the bottomsurface of the flexible roofing substrate, e.g., in a generally linearstripe. The sealant stripe can perform a number of sealing functions.For example, in one embodiment, the sealant stripe is positioned acrossthe bottom surface of the flexible roofing substrate such that when itis applied over another course of flexible roofing substrates in anarray, the sealant aligns with the lower edge of the shim on the topsurface of the headlap zone of the underlying flexible roofingsubstrate. In another embodiment, the sealant is provided near thedown-roof end of the flexible roofing element, so that the sealant wouldalign with the upper end of the photovoltaic element disposed on anunderlying flexible roofing substrate. In another embodiment, thesealant line is provided on the top surface of the flexible roofingsubstrate, for example, near the down-roof end of the shim, so that anoverlying flexible roofing element seals against it. The person of skillin the art will understand that the sealant stripe may be continuous ordiscontinuous, and may be formed in a variety of patterns on a surfaceof the shingle. The use of sealants is described further in U.S. patentapplication Ser. No. 12/560,724, which is hereby incorporated herein byreference in its entirety.

In another embodiment, the shingle has a shim disposed on its bottomsurface under the granule-coated zone. For example, FIG. 4 is aschematic side cross-sectional view of two courses of roofing productsas described herein. Shingles 400 a (shown in dotted line) are disposedso that they overlie shingles 400 b, as described above with respect toFIG. 3. Shingles 400 b have disposed in their granule-coated zones 414 bphotovoltaic elements 430 b, adhered thereto with the adhesive 440 b.The shims 422 b are disposed on the undersides of the shingles,underneath the granule-coated zones 414 b and extending into the headlapzones 418 b, and are of sufficient thickness so that the top surfaceplane 411 a of the shingles 400 a is at or above the top surface plane432 b of the photovoltaic elements 430 b. The person of skill in the artwill take into account the relative sizes of the headlap zone and theportion of the roofing substrate to remain uncovered by overlyingelements in determining the size of the shim.

In certain embodiments, a shim is provided both in the headlap zone, asdescribed above with reference to FIGS. 2 and 3, and underneath thegranule-coated zone, as described above with reference to FIG. 4. Thiscan provide even more thickness buildup for providing space for thephotovoltaic element while allowing proper drainage. The use of multipleshims can also provide design flexibility; for example, where theshingle does not receive a photovoltaic element, the shims can be usedto allow for slots or cutouts to provide a desired visual effect. Theperson of skill in the art will take into account the relative sizes ofthe headlap zone and the portion of the roofing substrate to remainuncovered by overlying elements in determining the sizes of the shims.

Roofing granules are familiar to the person of skill in the art. Theycan be, for example, ceramic-coated mineral particles, as areconventionally used in roofing applications. In certain embodiments, theroofing granules are of an average size of about 1-2 mm (e.g., about #11mesh). The roofing granules can be, for example, the same type, colorand distribution as those used in any other exposed roof area (e.g., aninactive area of the shingle, as described below), so that any exposedgranule-coated zones match the appearance of the rest of the roof.

Of course, a variety of types of roofing granules may be used inpracticing various aspects of the present invention. Roofing granulesmay be made from virtually any material that will withstand exposure tothe environment without substantially degrading over a period of years,e.g., rock, mineral, gravel, sand, ceramic, or plastic. In certainembodiments of the invention, the granules are ceramic-coated mineralcore particles optionally colored with metal oxides, such as thoseconventionally used on asphalt roofing shingles. The mineral core canconsist of any chemically inert matter that can support a ceramic layerand has adequate mechanical properties. The mineral particles, which canbe produced by a series of quarrying, crushing, and screeningoperations, are generally intermediate between sand and gravel in size(that is, between about 8 US mesh and 70 US mesh). In certainembodiments, roofing granules for use in the present invention have anaverage particle size of from about 0.2 mm to about 3 mm, and morepreferably from about 0.4 mm to about 2.4 mm. In particular, suitablysized particles of naturally occurring materials such as talc, slag,granite, silica sand, greenstone, andesite, porphyry, marble, syenite,rhyolite, diabase, greystone, quartz, slate, trap rock, basalt, andmarine shells can be used, as well as recycled manufactured materialssuch as crushed bricks, concrete, porcelain, ceramic grog, groundrecycled tires and fire clay.

Other materials, such as natural mineral matter (e.g., sand, crushedrock, and the materials listed above as suitable for the cores of coatedgranules), polymeric granules, and other synthetic materials can also beused. Polymeric materials, for example, can be provided with a varietyof shapes (e.g., spherical, angular, sub-angular), which can contribute,in whole or in part, to the desired appearance.

In certain embodiments, the granules can be relatively plate-like inshape (e.g., having one dimension that is at least half of the other twodimensions) to provide for more uniform surface coverage. Such granulescan be formed, for example, from slate. In certain embodiments, suchgranules can provide the desired distance between the tops of thegranules and the substrate surface, without having to be deeply embeddedinto the substrate material.

In certain embodiments, the granules are disposed on the roofingsubstrate in granule-coated zone (and/or in any inactive zones) with asurface fill factor of greater than about 60%. The surface fill factoris the fraction of the zone that is occluded by the granules, asmeasured in a direction normal to surface. Desirably, the granules havea surface fill factor of greater than about 75%. In certain desirableembodiments of the invention, the granules have a surface fill factor ofgreater than about 85%. Granule surface coverage can be measured usingimage analysis software, namely, Image-Pro Plus from Media Cybernetics,Inc., Silver Spring, Md. The shingle surface area is recorded in a blackand white image using a CCD camera fitted to a microscope. The image isthen separated into a bituminous coating portion and a granule coveringportion using the threshold method in gray scale. The amount of granulecoverage is then calculated by the image analysis software based uponthe number of pixels with gray scale above the threshold level dividedby the total number of pixels in the image. As the person of skill willrecognize, in certain embodiments relatively high surface fill factorscan be used across the entire roofing product, or in other embodiments,substantially only in the exposure area of the roofing product.

More than one type of granule can be used in the granule-coated zone.For example, a combination of larger (e.g., #11 mesh) and smaller (e.g.,#18 or #22 mesh) granules can be used.

The roofing granules can, for example, be solar reflective granules.Solar-reflective granules can be used, for example, in areas of theroofing product that are to remain exposed to the atmosphere when astructure or device is adhered. The solar-reflective roofing granulescan, for example, be coated over the entire exposed area of the roofingproduct, or alternatively only in the exposed area that is not to becovered with devices or structures, with the areas to be covered coatedwith less reflective roofing granules. The solar-reflective roofinggranules can operate to reflect a portion of the solar radiation (e.g.,in the infrared wavelengths) and thereby decrease the buildup of heat onthe roof. The effective working temperatures of the roof can thereby belowered, which can be advantageous in maintaining structures on the roofat a desirably low temperature. The solar-reflective roofing granulescan be disposed on the bituminous roofing substrate in an amountsufficient to provide the zone so coated with a solar reflectivitygreater than about 0.25. In one embodiment of the invention, thesolar-reflective roofing granules have a solar reflectivity greater thanabout 0.3, or even greater than about 0.4. Solar reflectance can reducethe effective temperature of the roof surface, which can improve theefficiency of power generation of the photovoltaic elements disposedthereon, as described in U.S. Patent Application Publication no.2009/0133738, which is hereby incorporated herein by reference in itsentirety. In some embodiments, the top surface of the bituminous roofingsubstrate is not coated with solar-reflective granules in the one ormore over-pressed zones (e.g., those that are to be covered by anelement or structure), resulting in more economical use of solarreflective coating or solar reflective roofing granules. Similarly, insome embodiments, the solar reflective granules do not extend to areasof the roofing product which are not visible when installed (e.g., theheadlap region of a shingle, or the selvage region of a roofingmembrane).

In certain embodiments, the granule-coated zone covers the entire areaof the roofing substrate that is not to be covered by overlying roofingsubstrates when installed, as described above with respect to FIG. 1. Inother embodiments, the granule-coated zone does not cover the entirearea of the roofing substrate that is not to be covered by overlyingroofing substrates when installed. In such embodiments, an inactive zoneis adjacent the granule-coated zone. The inactive zone can be coveredwith granules as well, but is different in some property than thegranule-coated zone. For example, the granules themselves can bedifferent, the way the granules are embedded in the roofing substratecan be different, and/or there can be a difference in coatings or othermaterials between the two zones. For example, as shown in top view inFIG. 5, flexible roofing substrate 500 is an asphalt shingle 510 havingthree tabs 506 extending from headlap zone 518. Each tab has a granulecoated zone 514 thereon, but each granule-coated zone does not cover theentire tab. Rather, each tab includes an inactive zone 515 surroundingthe granule-coated zone 514. The inactive zone has some propertydifferent from the granule-coated zone. For example, in certainembodiments, the inactive zones are coated with solar-reflectivegranules, whereas the granule-coated zones are coated with conventionalroofing granules. In other embodiments, the granules in thegranule-coated zone are embedded in the material of the roofingsubstrate more deeply than are the granules in the in the inactive zone.

In some embodiments of the invention, the surfacing of the one or moregranule-coated zones is selected so that the appearance of thegranule-coated zone is complementary to the top surface of the flexibleroofing substrate in the area adjacent to the granule-coated zone (e.g.,in an inactive area), and/or to the top surface of another roofingelement on the roof (e.g., a conventional roofing shingle, and/orroofing materials disposed at the ridge of the roof). As used herein L*,a* and b* are the color measurements for a given sample using the 1976CIE color space. The strength in color space E* is defined asE*=(L*²+a*²+b*²)^(1/2). The total color difference ΔE* between twoarticles is defined as ΔE*=(ΔL*²+Δa*²+Δb*²)^(1/2)) in which ΔL*, Δa* andΔb* are respectively the differences in L*, a* and b* for the twoarticles. L*, a* and b* values are measured using a HunterLab ModelLabscan XE spectrophotometer using a 0° viewing angle, a 45°illumination angle, a 10° standard observer, and a D-65 illuminant.Lower L* values correspond to relatively darker tones. In suchembodiments, if part or all of a granule-coated zone is not covered by aphotovoltaic element, it can complement the rest of the exposed surfaceof the flexible roofing substrate and/or the top surface of anotherroofing element on the roof. In certain embodiments of the invention,the granule-coated zone has a ΔE*<30 compared to the top surface of theflexible roofing substrate in the area adjacent to the granule-coatedzone and/or to the top surface of another roofing element on the roof.In some embodiments, the granule-coated zone has a ΔE*<20 compared tothe top surface of the flexible roofing substrate in the area adjacentto the granule-coated zone and/or to the top surface of another roofingelement on the roof. For example, the granule-coated zone can be coatedwith granules of similar color and distribution as those used in thearea adjacent to the granule-coated zone and/or on the top surface ofanother roofing element on the roof.

As described above, in certain embodiments of the invention, the topsurface of the flexible roofing substrate in the granule-coated zone isrecessed from the top surface of the flexible roofing substrate in thearea adjacent to the granule-coated zone (e.g., in an inactive zone). Inone such embodiment, the top surface of the flexible roofing substratein the granule-coated zone is recessed from the top surface of theflexible roofing substrate in an inactive zone. For example, as shown inpartial schematic cross-sectional view in FIG. 6, flexible roofingsubstrate 610 has a top surface 612. The top surface of the flexibleroofing substrate in the granule-coated zone 614 is recessed from thetop surface of the flexible roofing substrate in the area 615 adjacentto the granule-coated zone 614. In certain such embodiments, when aphotovoltaic element is disposed in the granule-coated zone, its topsurface can be substantially flush with the top surface of the areaadjacent to the granule-coated zone. The granule-coated zone can berecessed from the area adjacent thereto by, for example, at least about1 mm, or even at least about 2 mm. In certain embodiments, thegranule-coated zone is recessed from the area adjacent thereto by adistance in the range of about 65% to about 150% of the thickness of thephotovoltaic element to be used with the roofing product.

In certain embodiments, the granules in the granule-coated zones can beembedded in the bituminous material in the granule-coated zones so as tohave 0.20 gram loss or less in a rub test as described in ASTM D-4977.When there exists an inactive area, the granules in the inactive areacan, in certain embodiments, be embedded in the bituminous material soas to have substantially greater than 0.20 gram loss or less in a rubtest as described in ASTM D-4977, for example, 0.3 or greater, or even0.4 or greater. The ASTM D-4977 standard is hereby incorporated hereinby reference in its entirety.

In another embodiment, the granules in the granule-coated zones areembedded in the bituminous material so that the average granule embedvolume fraction is at least 50%. That is, each granule is embedded suchthat a certain fraction of its volume is lower than the surface of thebituminous material; this fraction is its embed volume fraction.According to this embodiment of the invention, the average embed volumefraction for all granules in the granule-coated zones is at least 50%.For example, the average granule embed volume fraction in thegranule-coated zones can be at least 60%, at least 70%, or even at least85%. When there exists an inactive area, the average granule embedfraction in the inactive area can be, for example, substantially lessthan 50%. For example, the average granule embed fraction in theinactive zone can be less than 45%, less than 40%, or even less than30%.

In certain embodiments, the roofing granules in the granule-coated zoneare pressed into the bituminous material more than are the roofinggranules in the inactive areas of the roofing substrate. For example, asshown in schematic cross-sectional view in FIG. 7, a flexible roofingsubstrate 710 formed from a bituminous material 712 has a granule-coatedzone 714 and an inactive zone 715. The inactive zone, for example, canframe the granule-coated zone (e.g., as shown in FIG. 5). As isconventional in bituminous roofing materials, roofing granules 782 aredisposed on the surface of the bituminous material in the inactive zone.In the granule-coated zone, roofing granules 784 are also disposed onthe surface of the bituminous material, but they are embeddedsubstantially more deeply in the bituminous material than are thegranules in the inactive area. For example, as shown in FIG. 7, thedistance between the average top of the granules and the surface of thebituminous material can be substantially greater in the inactive area(“A”) than in the granule-coated zone (“B”). The granules in thegranule-coated zones can be pushed more deeply into the bituminousmaterial in the granule coating process, for example, by first coatingboth the inactive areas and the granule-coated zones with granules as isconventional, then, while the bituminous material is still soft, pushingthe granules down farther only in the granule-coated zones. The secondpressing operation can also be performed with a separate heating of thesubstrate to soften the bituminous material. Alternatively, a granulepress with the desired surface relief can be used in the initial coatingprocess.

When the granules are embedded relatively deeply in the bituminousmaterial, the bituminous material can more strongly interact with thematerial of the photovoltaic element and/or an adhesive, providing astronger bond than when the photovoltaic element and/or adhesivesubstantially interacts only with the granules. This embodiment of theinvention can be especially advantageous when used in conjunction with apressure sensitive adhesive. Moreover, the reduced distance between thetop of the granules and the top of the bituminous material can in manycircumstances provide increased contact between an adhesive and thesurface of the granule-coated zone (e.g., when the adhesive is notfree-flowing). Bituminous roofing products with relativelydeeply-embedded substrates are described in more detail in U.S.Provisional Patent Application Ser. No. 61/358,703, which is herebyincorporated by reference in its entirety.

In certain embodiments, when the adhesive is provided on thegranule-coated zone (or is applied on the granule-coated zone some timebefore the photovoltaic elements are applied), the adhesive is coveredby a releasable liner. For example, as shown in partial schematiccross-sectional view in FIG. 8, roofing product 800 includes flexibleroofing substrate 810, which has a top surface 812 having agranule-coated zone 814. Disposed on the top surface 812 in part of thegranule-coated zone 814 is adhesive 842 covered by a releasable liner844. In such embodiments, the releasable liner can be removed (e.g., bypeeling using pull tab 846) to expose the adhesive material, which canbe used to affix a photovoltaic element to the granule-coated zone. Thereleasable liner can be, for example, release-coated paper. The adhesivematerial can be, for example, a pressure sensitive adhesive such as afunctionalized EVA-based pressure-sensitive adhesive (e.g., HP Fuller9917). The adhesive can, for example, be disposed in the granule-coatedzone of an already-installed roofing product in one operation, then aphotovoltaic element adhered can be thereto in a subsequent operation.In other embodiments, the adhesive is provided on the roofing productbefore installation.

In some embodiments of the invention, the surfacing of the one or moregranule-coated zones includes one or more alignment marks (e.g., printedor embossed) to aid in the alignment and installation of a photovoltaicelement. For example, the alignment marks can correspond with thevisible separations between sets of photovoltaic cells in thephotovoltaic element. In other embodiments, the alignment marks cancorrespond with markings formed on the top surface and/or the bottomsurface (e.g., the bottom surface of an adhesive layer) of thephotovoltaic element. In other embodiments, the alignment marks cancorrespond to markings formed on a surface of a releasable liner (e.g.,the surface in contact with an adhesive layer, or the bottom surface);as the releasable liner is removed to expose the adhesive layer (e.g.,when the photovoltaic element is supplied in roll form), the installercan use it as a guide to ensure alignment of the photovoltaic element tothe granule-coated zone. The use of alignment marks can be especiallyuseful when using photovoltaic elements in strip form, as the potentialfor alignment is higher for long, thin strips (e.g., United Solar Ovonicstrip photovoltaic element). The use of alignment marks in thegranule-coated zone can be especially useful when the photovoltaicelement is smaller than the granule-coated zone, so that the alignmentmarks are visible when the photovoltaic element is disposed thereon.

In other embodiments, the flexible roofing substrate includes one ormore alignment marks (e.g., printed or embossed) in an area adjacent thegranule-coated zone to aid in the alignment and installation of aphotovoltaic element. The alignment marks can be as described above forthe alignment marks in the granule-coated zone. For example, thealignment marks can correspond with the visible separations between setsof photovoltaic cells in the photovoltaic element. In other embodiments,the alignment marks can correspond with markings formed on the topsurface of the photovoltaic element. When the flexible roofing substrateis a shingle, the alignment marks can be, for example, in the headlaparea.

In one embodiment, the flexible roofing substrate is a roofing membrane,such as the type used in multiple layer or built-up roofing systems. Insuch embodiments, the flexible roofing substrate can be provided, forexample, as elongated sheets, which can be transported to the worksitein roll form. The roofing membrane can be, for example, formed from abituminous material, and can be reinforced with fibers, glass mat, felt,or fabric, and coated with roofing granules as described herein. Inother embodiments, the roofing membrane can be formed from a rubber orpolymeric material. Installation of the membrane can be performedthrough a variety of mechanical fasteners, adhesives, torching, or anyother suitable methods. Adjacent sheets of roofing membrane can besealed together where they adjoin. The roofing membranes of the presentinvention can be installed together with conventional roofing membraneproducts, to provide only certain areas of the roof with photovoltaicpower generation capability. Roofing membranes can be formed, forexample, from a single sheet of material with different surfacingsformed thereon, or can be formed by combining sheets of materialside-by-side so as to make a single membrane having differentsurfacings.

In another embodiment, the flexible roofing substrate is a shingle. Forexample, the shingle can be formed from a bituminous material, which canbe reinforced with fibers, glass mat, felt, or fabric, and coated withroofing granules (e.g., in areas outside of the granule-coated zones).Shingles can, for example, be provided in product constructions thathave a single layer of bituminous shingle material. In otherembodiments, multilayer laminated shingle constructions can be used.Laminated shingles can provide for a wide range of aesthetic effects inshingle design, as well as provide space within the shingle toaccommodate wiring and electrical connector structures. For example, asthe person of skill in the art will appreciate, a backing shim can beused to provide an aesthetic effect delineating any tabs on the shingle,and/or create the illusion of shadows and structure, as well asproviding another layer of material to cover a roof. The backing shimcan underlay the entire shingle, or alternatively can underlay only partof the shingle. Laminated shingles can also yield a flatter layingproduct without undesirable bumps when installed. Examples of suitableshingle designs and constructions include those available fromCertainTeed Corporation, including, for example, the Centennial Slate™shingle and the Hatteras® shingle. Shingles can be manufactured, forexample, using conventional methods, and cut into individual pieces.Shingles can be provided in bundles to a worksite, and can be installedusing mechanical fasteners or other suitable methods. Adjacent coursesof shingles can be applied in an overlapping manner to cover and protectthe roof. The shingles of the present invention can be installedtogether with conventional shingles, to provide only certain areas ofthe roof with photovoltaic power generation capability.

The one or more granule-coated zones can be provided on the flexibleroofing substrate in a wide variety of geometries. For example, they canbe provided as islands or isolated zones (e.g., as described above withrespect to FIG. 5); or alternatively can extend the length of a flexibleroofing substrate (e.g., as described above with respect to FIG. 1). Forexample, in one embodiment, as shown in FIG. 9( a), the granule-coatedzones 914 a are formed as isolated zones on the top surface of a roofingmembrane 910 a. In another embodiment, as shown in FIG. 9( b), agranule-coated zone 914 b is formed to continuously extend along thelength of a roofing membrane 910 b, as shown in FIG. 9( b). In otherembodiments, the granule-coated zone 914 c is formed to cover the entiresurface of a roofing membrane 910 c except for one or more selvage zones917 b and 917 c formed along one or more edges, as shown in FIGS. 9( b)and 9(c).

In certain embodiments, the flexible roofing substrate has a height(i.e., measured in the direction going up the roof as installed) ofabout eighteen inches (for example, in the range of 17 inches to 19inches, in the range of 17.5 inches to 18.5 inches, or even in the rangeof 17.7 inches to 18.3 inches). One such embodiment is shown in FIG. 10;flexible roofing substrate 1010 is a shingle having a height “H” ofabout 18 inches. For example, a shingle dimension of 18″×36″ can beused. In certain embodiments, the flexible roofing substrate can have anexposure area (i.e., the area exposed as installed) having exposureheight (i.e., height of the exposed area as installed, shown as “E” inFIG. 10) of about eight inches (for example, in the range of 7 inches to9 inches, in the range of 7.5 inches to 8.5 inches, or even in the rangeof 7.7 inches to 8.3 inches). The flexible roofing substrate can, forexample, be a shingle having multiple tabs in its exposure area, asshown in FIG. 10, or can be substantially continuous. As the person ofskill in the art will appreciate, the shingle can be of single- ormultiple layer construction. In certain embodiments, the one or moregranule-coated zones of the flexible roofing substrate area are disposedsubstantially within the exposure area. In one embodiment, the one ormore granule-coated zones can have a height (shown as “G” in FIG. 10) ofabout eight inches (for example, in the range of 7 inches to 9 inches,in the range of 7.5 inches to 8.5 inches, or even in the range of 7.7inches to 8.3 inches). In certain embodiments, the granule-coated zonehas a height that is slightly less than or equal to (e.g., in the rangeof zero to one inch, in the range of zero to 0.5 inches, or even in therange of 0 to 0.3 inches less than) the height of the exposure area. Inother embodiments, the height of the granule-coated zone is somewhatgreater than (e.g., in the range of zero to 0.5 inches, or even zero to1.0 inches) the height of the exposure area.

The use of flexible roofing substrates having heights of about eighteeninches, optionally with exposure heights of about eight inches and/orgranule-coated zones having heights of about eight inches can result ina number of advantages. For example, such configurations can result indesirable natural-appearing effects, similar to those of certainstandard roofing shingles. Moreover, these configurations can requirerelatively few nails per square of roofing material, require theinstallation of relatively few flexible roofing elements per square ofroofing material, result in material and labor savings, allow for theready manufacture of flexible roofing substrates from sheets of materialthat are originally about 36 inches wide, and result in efficientloading on standard 36 inch pallets. Moreover, use of exposure areasand/or granule-coated zones having heights of about eight inches canresult in more efficient use of photovoltaic elements, as compared tosystems based on standard roofing elements having a twelve inch heightand an exposure area having a height of five inches, as fewer individualphotovoltaic elements are required to outfit an equivalent roof area.Similarly, less time can be spent installing and wiring photovoltaicelements as compared to systems based on standard roofing elementshaving a twelve inch height and an exposure area having a height of fiveinches, as fewer photovoltaic elements would need to be installed andfewer wiring connections would need to be made per unit area. Moreover,shingles substantially larger than eighteen inches in height can bedifficult for a single worker to handle on the roof with any windpresent. Use of roofing elements having heights of about eighteeninches, exposure zones having heights of about eight inches, and/orgranule-coated zones having heights of about eight inches, as describedabove, and/or photovoltaic elements having heights of about eightinches, as described in more detail below, can advantageously be used inconjunction with any appropriate embodiments described herein.

As noted above, the roofing product further includes an adhesivesuitable for securing a photovoltaic element to one or more of thegranule-coated zones. The adhesive is capable of forming a bond to thegranules and the top surface of the flexible roofing substrate and tothe bottom surface of the photovoltaic element. When it is applied tothe granule-coated zones, an adhesive desirably is of sufficient lengthand width to correspond to the dimensions of the lower surface of aphotovoltaic element, and is of sufficient thickness and character toprovide a suitable bond between the photovoltaic element and theflexible roofing substrate. Especially suitable adhesives providesufficient bond strength to join the bottom surface of the photovoltaicelement to the top surface of the flexible roofing substrate, and shouldbe able to withstand severe outdoor weathering. In one embodiment of theinvention, the adhesive provides greater than 10 lb/inch adhesive bondstrength in a 90° peel test. In certain embodiments, the adhesivemaintains the bond strength in severe outdoor conditions for an extendedperiod of time, e.g., 20 years of service life. The adhesive can, forexample, meet the humidity-freeze cycle test, thermal cycle test, anddamp-heat test requirements listed in IEC 1646. Moreover, in certainembodiments the materials of the adhesive can flexibly be incorporatedthrough use of a variety of adhesive processes.

In certain desirable embodiments, the adhesive can be applied to thegranule-coated zone of the roofing product such that it fills in betweenthe granules and forms a bond with the roofing product, as well as withthe photovoltaic element to be applied over it. In one embodiment, theadhesive sets at ambient conditions. In another embodiment, heat canoptionally be employed to accelerate the setting of the adhesive. Incertain embodiments, the rheological behavior of the adhesive is suchthat it flows into place and remains in position on the granule-coatedzone of the roofing product without slumping or sagging on a sloped roofinstallation, either before or after the installation of thephotovoltaic element. In some embodiments, the adhesive is applied tothe granule-coated zone of the roofing product surface in a liquid orsemiliquid state.

There are a great variety of adhesives that are suitable for use invarious embodiments and aspects of the present invention. For example,adhesive can be a self-adhesive tape (e.g., butyl, ethylene-propyleneadhesives); a reactive pressure sensitive adhesive including amicroencapsulated curing agent; or a settable adhesive such as anadhesive caulk like butyl adhesive, a two part reactive polyurethane, areactive epoxy, a room temperature vulcanizable silicone, a moisturecurable urethane, or the like. For example, U.S. Reissue Pat. No. RE39,764 discloses a one-part, moisture-curable, foaming polyurethaneadhesive useful for roof structures. U.S. Pat. No. 7,234,284 disclosesan adhesive for use in roofing construction comprising an asphalt, apolymer, a tackifier, and a plasticizer. United States PatentApplication Publication no. 2005/0246991A1 describes a one component,moisture curable, isocyanate terminated adhesive composition foradhering a polymeric sheet to a substrate. U.S. Pat. No. 6,852,185discloses a method of securing shingles to a roof with a two partpolyurethane adhesive. U.S. Pat. No. 5,872,203 describes a 100% solidspolyurethane adhesive composition for bonding polymeric roofingmaterials to roof-deck substrates which includes two components. U.S.Pat. No. 5,421,876 discloses a solvent free, organo-clay filledasphaltic polyurethane dispersion that is stable and moisture curable toan elastomer having excellent adhesion and weather resistance especiallyused as roofing adhesive. U.S. Pat. Nos. 4,755,545, 4,923,913 and5,011,726 disclose bituminous adhesives that can be used with roofingshingles. International Patent Application Publication no. WO83/00520A1discloses a curable silicone elastomer based roofing system. U.S. Pat.No. 4,026,853 discloses a curable bituminous organosiloxane composition.U.S. Pat. No. 3,980,597 discloses a moisture curable polyurethanesealant composition suitable for roofs. U.S. Pat. No. 3,637,558discloses elastomeric compositions from asphalt and partially uncuredurethanes of allylic hydroxyl-terminated diene polymers. U.S. Pat. No.3,372,083 discloses compositions and articles from the reaction of anisocyanate terminated polyurethane and the isocyanate adduct of bitumen.Certain suitable adhesives are described in U.S. Patent ApplicationPublication no. 2009/0133340 A1. Each of the above-referencedpublications and patents is hereby incorporated herein by reference inits entirety.

The adhesive can be applied to the flexible roofing substrate in avariety of ways. For example, an applicator can be used to deliverliquid adhesive components to the flexible roofing substrate. In anexample of an applicator for a two-part adhesive, two cartridgesseparately deliver reactive components through a funnel portion to astatic mixer and then to a nozzle of appropriate dimension to correspondto the width of the photovoltaic element. U.S. Pat. No. 4,253,566, whichis hereby incorporated by reference in its entirety, discloses aresin-containing cartridge system capable of mixing and applying amulticomponent reactive adhesive system. It will also be understood thata one component adhesive could also be used with an appropriateapplicator. The adhesive could be a moisture cure adhesive that beginsto cure once it is applied to the flexible roofing substrate. Theadhesive could also comprise a two part adhesive package where one partis applied to the flexible roofing substrate with an applicator and theother part is applied to the bottom surface of the photovoltaic element,the two parts reacting when photovoltaic element is brought togetherwith the flexible roofing substrate. In other embodiments, the adhesiveis manually applied to the flexible roofing substrate.

In certain embodiments, the adhesive is provided as part of thephotovoltaic element, for example, as a release liner-covered layer onthe bottom of the photovoltaic element. In other embodiments, theadhesive is separate, and applied separately to the flexible roofingsubstrate.

In another aspect, the adhesive is applied to the granule-coated zone ofthe roofing product surface as a preformed conformable adhesive strip.In certain embodiments, the adhesive has a composite structurecomprising a layer of pressure sensitive adhesive and a layer ofdeformable material. For example, the deformable material can besandwiched between layers of adhesive material. The deformable materialcan allow for more economical usage of a higher performance, higher costpressure sensitive adhesive. The use of deformable layers to improvecontact between pressure sensitive adhesives and irregular surfaces isdisclosed in U.S. Pat. No. 5,310,278, which is hereby incorporatedherein by reference in its entirety. The adhesive materials can besupplied as a transfer adhesive protected with a releasable liner; thereleasable liner can be removed (e.g., by peeling) to expose theadhesive for attachment to the granule-coated zone surface of theflexible roofing substrate. In one embodiment, the structure has tworelease liners; one protecting the top adhesive surface and the otherprotecting the bottom adhesive surface. In another embodiment, theself-adhesive layer has a single dual release liner such that, whenprovided in a roll form (for example), the protective liner issandwiched between the top adhesive surface of one layer of the roll andthe bottom adhesive surface of an adjacent layer of the roll.Alternatively, a single liner can be folded around the structure tocover both top and bottom adhesive surfaces. In use, an adhesive surfaceis pressed into intimate contact with the granule-coated surface to bondwith the flexible roofing substrate. The thickness of and deformablenature of the interlayer between the top and bottom adhesive materialsallows for good contact between the adhesive and the granule coveredflexible roofing substrate. The remaining release liner is removed andthe photovoltaic module is adhered thereto, for example, in a separateoperation occurring some time after the adhesion of the structure to thegranule-coated zone of the roofing substrate. Optionally, thephotovoltaic module may include another adhesive material on the bottomsurface thereof. The chemistry of the upper and lower adhesive surfacesof the self-adhesive layer may be the same or different. U.S. Pat. No.4,273,827, which is hereby incorporated herein by reference in itsentirety, discloses a preformed adhesive assembly suitable forattachment of disparate surfaces on to another. Similarly, U.S. Pat. No.4,356,676, which is hereby incorporated herein by reference in itsentirety, describes a preformed conformable adhesive structure.

A preformed adhesive structure that is commercially available isEternaBond DoubleStick® from EternaBond (Mundelein, Ill.). The selfsealing adhesive is used to create a water tight, conformable sealbetween two or more irregular surfaces and/or a weather proof, permanentbond between two or more similar or dissimilar surfaces. The tapeutilizes a 100% solids formulation of synthetic resins, thermoplastics,non-curing rubbers, with a built in primer, sandwiched between twosiliconized release liners. Optionally, a primer may be applied to thesurface of the granule covered flexible roofing substrate prior toapplication of the DoubleStick® tape. The first liner is stripped fromthe tape and it is applied to the granule-coated roofing substrate andtamped in place. The second liner is removed and a photovoltaic elementis attached thereto.

An adhesive can act to adhere the photovoltaic element to thegranule-coated zone of the flexible roofing element when they are formedof partially incompatible materials (for example, when the photovoltaicelement is an encapsulated photovoltaic element having a fluoropolymerat its bottom surface). In one embodiment of the invention, the adhesiveconsists essentially of a single polymer layer having a surface tensionin the range of about 25% to about 75% of the way between the surfacetension value of the granule-coated zone of the roofing element and thesurface tension value of the bottom surface of the photovoltaic element.

In one embodiment of the invention, the adhesive includes a polymericmaterial having a Chang viscoelastic window exhibiting at least one setof coordinates (log(G″), log(G′)) lying within the window bound by thecoordinates (4.5, 3), (4.5, 6), (6, 6), (6, 3) (e.g., pressure sensitiveadhesives). In certain embodiments of the invention, the polymericmaterial has a Chang viscoelastic window exhibiting at least one set ofcoordinates (log(G″), log(G′)) lying within the window bound by thecoordinates (4.5, 6), (6, 6), (6, 3.7). In other embodiments of theinvention, the polymeric material has a Chang viscoelastic windowexhibiting at least one set of coordinates (log(G″), log(G′)) lyingwithin the window bound by the coordinates (4.5, 6), (4,5,8), (8, 8),(8, 3.7), (6, 3.7). In other embodiments of the invention, the polymericmaterial has a Chang viscoelastic window exhibiting at least one set ofcoordinates (log(G″), log(G′)) lying within the window bound by thecoordinates (4.5, 6), (4,5,8), (8, 8), (8,3.7), (6, 3.7), (6, 6). G″ isthe viscous shear modulus in units of Pa, and G′ is the elastic shearmodulus in units of Pa. G and G″ can be measured as described in ASTM882-97, for example at frequencies of 0.01 R/S and 100 R/S. Dissipativematerials generally have Chang viscoelastic window coordinates withinthe above-referenced windows. Such materials are described in moredetail in U.S. Pat. No. 6,869,981, and at pages 171-184 of Handbook ofPressure Sensitive Adhesive Technology, 3rd Ed., D. Satas editor, 1999,each of which is hereby incorporated herein by reference in itsentirety; the UV curable materials described therein can be converted toheat-curable materials by changing initiators. Other examples includeVHB adhesive materials available from 3M.

In certain embodiments of the invention, the adhesive has a coefficientof thermal expansion (“CTE”) between the CTE of the granule-coated zoneof the flexible roofing substrate and the CTE of the bottom surface ofthe photovoltaic element, measured at 100° F. In one embodiment of theinvention, the adhesive has a CTE in the range of about 25% to about 75%of the way between the CTE of the granule-coated zone of the flexibleroofing substrate and the CTE of the bottom surface of the photovoltaicelement, measured at 100° F. In one embodiment of the invention, thegranule-coated zone of the roofing element is bitumen-based with a CTEof ˜2.5×10⁻⁴ in/in/° F. As the person of skill will appreciate, thethermal expansion behavior of the granule-coated zone will be determinedchiefly by the material in which the granules are embedded, and not theindividual granules themselves.

In certain embodiments of the invention, the adhesive is not conductive.In such embodiments, the photovoltaic elements do not require additionalgrounding to prevent electric shock or to meet electrical coderequirements.

In other embodiments of the invention, the adhesive includes anamino-substituted organosilane layer, for example as described in U.S.Pat. No. 6,753,087, which is hereby incorporated herein by reference.For example, the adhesive can include a polymeric layer (e.g., havingpolar functionality) having blended therein an amino-substitutedorganosilane.

The thickness of the adhesive can be, for example, in the range of about25 μm to about 2.5 mm. In certain embodiments of the invention, thethickness of the adhesive is in the range of about 50 μm to about 1 mm.

Photovoltaic elements suitable for use in conjunction with the roofingproducts of the invention, and in the photovoltaic roofing elements,systems, methods and kits of the invention comprise one or moreinterconnected photovoltaic cells provided together in a single package.The photovoltaic cells of the photovoltaic elements can be based on anydesirable photovoltaic material system, such as monocrystalline silicon;polycrystalline silicon; amorphous silicon; III-V materials such asindium gallium nitride; II-VI materials such as cadmium telluride; andmore complex chalcogenides (group VI) and pnicogenides (group V) such ascopper indium diselenide. For example, one type of suitable photovoltaiccell includes an n-type silicon layer (doped with an electron donor suchas phosphorus) oriented toward incident solar radiation on top of ap-type silicon layer (doped with an electron acceptor, such as boron),sandwiched between a pair of electrically-conductive electrode layers.Another type of suitable photovoltaic cell is an indium phosphide-basedthermo-photovoltaic cell, which has high energy conversion efficiency inthe near-infrared region of the solar spectrum. Thin film photovoltaicmaterials and flexible photovoltaic materials can be used in theconstruction of photovoltaic elements for use in the present invention.In one embodiment of the invention, the photovoltaic element includes amonocrystalline silicon photovoltaic cell or a polycrystalline siliconphotovoltaic cell. The photovoltaic elements for use in the presentinvention can be flexible, or alternatively can be rigid.

The photovoltaic elements can be encapsulated photovoltaic elements, inwhich photovoltaic cells are encapsulated between various layers ofmaterial. For example, an encapsulated photovoltaic element can includea top layer material at its top surface, and a bottom layer material atits bottom surface. The top layer material can, for example, provideenvironmental protection to the underlying photovoltaic cells, and anyother underlying layers. Examples of suitable materials for the toplayer material include fluoropolymers, for example ETFE (“TEFZEL”), PFE,FEP, PVF (“TEDLAR”), PCTFE or PVDF. The top layer material canalternatively be, for example, a glass sheet, or a non-fluorinatedpolymeric material. The bottom layer material can be, for example, afluoropolymer, for example ETFE (“TEFZEL”), PFE, FEP, PVDF or PVF(“TEDLAR”). The bottom layer material can alternatively be, for example,a polymeric material (e.g., polyester such as PET); or a metallicmaterial (e.g., steel or aluminum sheet). In certain embodiments of theinvention, the photovoltaic element is built on a flexible steelsubstrate, as described, for example, in U.S. Pat. No. 5,457,057, whichis hereby incorporated by reference in its entirety. In suchembodiments, the photovoltaic cells can be formed from amorphoussilicon.

As the person of skill in the art will appreciate, an encapsulatedphotovoltaic element can include other layers interspersed between thetop layer material and the bottom layer material. For example, anencapsulated photovoltaic element can include structural elements (e.g.,a reinforcing layer of glass, metal or polymer fibers, or a rigid film);adhesive layers (e.g., EVA to adhere other layers together); mountingstructures (e.g., clips, holes, or tabs); one or more electricalconnectors (e.g., electrodes, electrical connectors; optionallyconnectorized electrical wires or cables) for electricallyinterconnecting the photovoltaic cell(s) of the encapsulatedphotovoltaic element with an electrical system. An example of anencapsulated photovoltaic element suitable for use in the presentinvention is shown in schematic exploded view and schematic crosssectional view in FIG. 11. Encapsulated photovoltaic element 1160includes a top protective layer 1152 (e.g., glass or a fluoropolymerfilm such as ETFE, PVDF, PVF, FEP, PFA or PCTFE); encapsulant layers1154 (e.g., EVA, functionalized EVA, crosslinked EVA, silicone,thermoplastic polyurethane, maleic acid-modified polyolefin, ionomer, orethylene/(meth)acrylic acid copolymer); a layer ofelectrically-interconnected photovoltaic cells 1156; and a backing layer1158 (e.g., PVDF, PVF, PET).

A photovoltaic element having a self-adhesive layer on its bottomsurface can be suitable for use in the present invention. In certainembodiments, such a photovoltaic element provides the adhesive thatadheres the photovoltaic element to the granule-coated zone. In otherembodiments, the adhesive of the photovoltaic element adheres to anadhesive already disposed in the granule-coated zone. In one example,the self-adhesive layer is a 3-10 mil thick layer of a butylrubber-based or rubber resin pressure sensitive adhesive. Suitablerubber resin pressure sensitive adhesives are disclosed, for example, inU.S. Pat. No. 3,451,537, which is hereby incorporated herein byreference in its entirety. Other photovoltaic elements and adhesivesystems suitable for use in the present invention are described in U.S.Pat. Nos. 6,729,081 and 6,553,729, each of which is hereby incorporatedherein by reference in its entirety. In certain embodiments, theadhesive on the bottom surface of the photovoltaic element has acomposite structure comprising a layer of pressure sensitive adhesiveand a layer of deformable material. The deformable material can allowfor more economical usage of a higher performance, higher cost pressuresensitive adhesive. The use of deformable layers to improve contactbetween pressure sensitive adhesives and irregular surfaces is disclosedin U.S. Pat. No. 5,310,278, which is hereby incorporated herein byreference in its entirety. The self-adhesive layer can be protected witha releasable liner; the releasable liner can be removed (e.g., bypeeling) to expose the adhesive for attachment to the granule-coatedzone of a flexible roofing substrate.

The photovoltaic element can include at least one antireflectioncoating, for example as the top layer material in an encapsulatedphotovoltaic element, or disposed between the top layer material and thephotovoltaic cells. In other embodiments, the photovoltaic element caninclude, for example, a lenticular element, such as that described inInternational Patent Application Publication no. WO 2007/085721, whichis hereby incorporated herein by reference in its entirety; or adecorative and/or colored overlay, such as that described in U.S. PatentApplication Publication no. 2009/0000221, which is hereby incorporatedherein by reference in its entirety. The removable cover elements can beremoved after installation to expose the photovoltaically active areas.Moreover, in embodiments in which a roofing coating is disposed on roof(e.g., as described below with reference to FIG. 19), the removablecover elements can be removed after the roofing coating is applied. Insuch embodiments, the roofing coating can be applied over the entireroof, and can help to waterproof the seams between the photovoltaicelements and the flexible roofing substrates.

Suitable photovoltaic elements can be obtained, for example, from ChinaElectric Equipment Group of Nanjing, China, as well as from severaldomestic suppliers such as United Solar Ovonic, Sharp, Shell Solar, BPSolar, USFC, FirstSolar, General Electric, Schott Solar, Evergreen Solarand Global Solar. Moreover, the person of skill in the art can fabricateencapsulated photovoltaic elements using techniques such as laminationor autoclave processes. Encapsulated photovoltaic elements can be made,for example, using methods disclosed in U.S. Pat. No. 5,273,608, whichis hereby incorporated herein by reference.

The top surface of a photovoltaic element is the surface presenting thephotoelectrically-active areas of its one or more photoelectric cells.When installed, the photovoltaic roofing elements of the presentinvention should be oriented so that the top surface of the photovoltaicelement is able to be illuminated by solar radiation. The bottom surfaceis the surface opposite the top surface.

The photovoltaic element also has an operating wavelength range. Solarradiation includes light of wavelengths spanning the near UV, thevisible, and the near infrared spectra. As used herein, the term “solarradiation,” when used without further elaboration means radiation in thewavelength range of 300 nm to 2500 nm, inclusive. Different photovoltaicelements have different power generation efficiencies with respect todifferent parts of the solar spectrum. Amorphous doped silicon is mostefficient at visible wavelengths, and polycrystalline doped silicon andmonocrystalline doped silicon are most efficient at near-infraredwavelengths. As used herein, the operating wavelength range of aphotovoltaic element is the wavelength range over which the relativespectral response is at least 10% of the maximal spectral response.According to certain embodiments of the invention, the operatingwavelength range of the photovoltaic element falls within the range ofabout 300 nm to about 2000 nm. In certain embodiments of the invention,the operating wavelength range of the photovoltaic element falls withinthe range of about 300 nm to about 1200 nm.

In certain embodiments, the photovoltaic elements are provided withremovable cover elements covering their photovoltaically-active areas,as described in United States Patent Application Publication no.2009/0000221, which is hereby incorporated herein by reference in itsentirety. The removable cover elements can be removed after installationto expose the photovoltaically active areas.

Another embodiment of the invention is a photovoltaic roofing element,including the roofing product as described above, with the adhesivedisposed in one or more of the granule-coated zones. One or morephotovoltaic elements is disposed on the adhesive in the one or moregranule-coated zones of the top surface of the flexible roofingsubstrate. In certain embodiments, at least some of the granule-coatedzones remain exposed as exposure zones. One embodiment is shown in topschematic view in FIG. 12, and in schematic cross-sectional view in FIG.13. Photovoltaic roofing element 1205 includes flexible roofingsubstrate 1210, which has a granule-coated zone 1214. Disposed in thegranule-coated zone 1214 is adhesive 1242, which adheres photovoltaicelement 1260 to the flexible roofing substrate. In this embodiment, aportion 1219 of the granule-coated zone remains exposed as an exposurezone.

While in many embodiments the adhesive is sufficient to hold thephotovoltaic element in place on the flexible roofing substrate, it canoften be desirable to use a mechanical fastener is used together withthe adhesive in the attachment of the photovoltaic elements to theflexible roofing substrate. The mechanical fastener can be, for example,nails, staples, screws, clips or the like; such fasteners can attach thephotovoltaic element only to the flexible roofing substrate on which itis disposed, or can go through the flexible roofing substrate down tounderlying flexible roofing substrates, or even through to the roof deckitself. The mechanical fastener can provide for additional security ofattachment of the photovoltaic element under conditions of steep slopeor high temperature, where an adhesive may be subject to shear stresses.The mechanical attachment can be particularly helpful on the lower edgeof the photovoltaic element to prevent sliding movement down the roof.Moreover, mechanical attachment at the lower edge may impart addedresistance to wind uplift detachment of the photovoltaic element or theflexible roofing substrate. Mechanical attachment at one edge of thephotovoltaic element can also allow a degree of movement within the tielayer system to accommodate differential thermal expansion andcontraction between the photovoltaic element and the flexible roofingsubstrate.

In some embodiments, the photovoltaic element will include fasteningtabs or a fastening zone (e.g., a marked area) to aid in the attachmentof the photovoltaic element to the granule-coated zone of the flexibleroofing substrate. Fastening zones and tabs may be configured using aflexible material, such as described in U.S. Pat. Nos. 5,729,946,5,857,303, 5,887,743, 5,857,303 and 6,000,185, each of which is herebyincorporated by reference in its entirety. Flexible fastening zones canhelp to accommodate movement between the photovoltaic element and theflexible roofing substrate, for example due to differential thermalexpansion. For example, in one example of a photovoltaic roofing element1405 of the invention, shown in top schematic view in FIG. 14,photovoltaic element 1460 (having photovoltaically active area 1463) isdisposed in the granule-coated zones of flexible roofing substrate 1410.Photovoltaic element 1460 includes both fastening tabs 1461 and afastening zone 1462. The fastening tabs 1461 and fastening zone 1462denote places that where fastening will cause no damage to thephotovoltaic element (e.g., areas devoid of photovoltaic cells orelectrical components such as wiring). The fastening tabs can in someembodiments be covered by an overlying course of flexible roofingsubstrates (e.g., shingles). In certain embodiments, the photovoltaicelement includes fastening tabs (e.g., as denoted by 1461 in FIG. 14),but no other fastening zone.

In certain embodiments of the photovoltaic roofing elements, more thanone photovoltaic element is disposed on each granule-coated zone. Forexample, a photovoltaic roofing element 1505 according to one embodimentof the invention is shown in top schematic view in FIG. 15. Photovoltaicroofing element includes a roofing membrane 1510, with a granule-coatedzone 1514 that covers the entire membrane except for two edges 1517 (forexample, as described above with respect to FIG. 9). Three photovoltaicelements 1560 (e.g., in the form of strips of encapsulated photovoltaicelements) are adhered to the single granule coated zone 1514 with anadhesive (not shown). In certain embodiments, and as shown in FIG. 15,the photovoltaic elements can be arranged with some exposed area betweenthem; in such embodiments, the granule-coated zone can provide a desiredappearance and weather durability to the exposed area betweenphotovoltaic elements. In other embodiments, the photovoltaic elementscan be contiguously arranged.

In other embodiments, a single photovoltaic element extends acrossmultiple granule-coated zones. For example, in the embodiment shown intop schematic view in FIG. 16, photovoltaic roofing element 1605includes a flexible roofing substrate 1610, which includes a pluralityof tabs 1606 extending from headlap zone 1618. Each tab 1606 has agranule-coated zone 1614 formed thereon. A photovoltaic element 1660 isadhered to the four granule coated zones 1614 with an adhesive (notshown). The photovoltaic element can be, for example, a strip of fourelectrically interconnected T-cell photovoltaic elements in a laminatestructure, with a pressure-sensitive adhesive on the bottom surface ofthe laminate structure.

In certain photovoltaic elements of the invention, at least about 70%,at least about 80%, or even at least about 90% of the totalgranule-coated zone area of a flexible roofing substrate is covered byphotovoltaic elements.

In embodiments in which multiple photovoltaic elements are disposedadjacent to one another in a granule-coated zone, waterproofing may beprovided via an optional bead of an adhesive, caulk or other sealantbetween adjacent photovoltaic elements. Alternatively, a pressuresensitive adhesive tape with a backing layer stabilized for outdoorperformance can be used to seal the seams between adjacent photovoltaicelements.

In certain embodiments, the flexible roofing substrate of thephotovoltaic roofing element has a height of about eighteen inches, asdescribed above. In certain such embodiments, the flexible roofingelement has an exposure area having an exposure height of about eightinches, as described above; one or more granule-coated zones having aheight of about eight inches, as described above; or both. Thephotovoltaic element can similarly have a height (measured in thedirection going up the roof as installed) of about eight inches (forexample, in the range of 7 inches to 9 inches, in the range of 7.5inches to 8.5 inches, or even in the range of 7.7 inches to 8.3 inches).The use of photovoltaic elements having heights of about eight inchescan result in more efficient use of photovoltaic elements, as comparedto systems based on standard roofing elements having a twelve inchheight and an exposure area having a height of five inches, as fewerphotovoltaic elements are required to outfit an equivalent roof area.Similarly, less time can be spent installing and wiring photovoltaicelements as compared to systems based on standard roofing elementshaving a twelve inch height and an exposure area having a height of fiveinches, as fewer photovoltaic elements would need to be installed andfewer wiring connections would need to be made per unit area. Moreover,shingles substantially larger than eighteen inches in height can bedifficult for a single worker to handle on the roof with any windpresent. Similarly, photovoltaic elements eight inches in height(especially in roll form) can be of a convenient size for handling on aroof, especially on a pitched roof where balance can be difficult makinglarger photovoltaic elements unwieldy. Moreover, photovoltaic elementshaving a height of about eight inches can be conveniently fabricatedfrom a roll of flexible steel material (see, e.g., U.S. Pat. No.5,457,057) having a width of about 15 inches; amorphous silicon-basedcells can be deposited onto the flexible steel material, which can becut lengthwise into about 7.5 inch wide strips, which when packaged andencapsulated can be about eight inches in height. Accordingly,photovoltaic elements about eight inches in height can efficiently usethe entire width of the 15 inch flexible steel substrate commonly usedin the fabrication of photovoltaic devices.

An example of such a photovoltaic roofing element is shown in topschematic view in FIG. 17. Photovoltaic roofing element 1705 includes aroofing substrate 1710, which has a height “H” of about 18″ (e.g., inthe range of 17 inches to 19 inches, in the range of 17.5 inches to 18.5inches, or even in the range of 17.7 inches to 18.3 inches), and a topsurface having an exposure area of height “E” of about eight inches(e.g., in the range of 7 inches to 9 inches, in the range of 7.5 inchesto 8.5 inches, or even in the range of 7.7 inches to 8.3 inches).Disposed in the exposure area (in a granule-coated zone, adhered withadhesive, not shown) is photovoltaic element 1760 having a height “P” ofabout eight inches (e.g., in the range of 7 inches to 9 inches, in therange of 7.5 inches to 8.5 inches, or even in the range of 7.7 inches to8.3 inches). Of course, in other embodiments, the photovoltaic roofingelement can be built with “tabs,” as is conventional in the art andshown in FIGS. 5, 10 and 16, or in some other configuration.

Another embodiment of the invention is shown in top schematic view inFIG. 18. Photovoltaic roofing element 1805 includes a flexible roofingsubstrate 1810, having an overall height “H”, an exposure area 1812having a height “E”, and a headlap area 1818. One or more photovoltaicelements 1860, having height “P” are disposed (in a granule-coated zone,adhered with adhesive, not shown) in the exposure area. The photovoltaicelements 1860 can be interconnected, for example, by jumper wires 1862.The photovoltaic roofing element can have electrodes on its bottomsurface for interconnection into a larger electrical system;alternatively, one or more optionally connectorized input/output cablescan be used to collect the energy generated by the photovoltaicelement(s). The photovoltaic roofing element also includes anencapsulant layer 1870 disposed over the exposure area, covering boththe photovoltaic elements and the exposed inactive regions of theexposure area. The encapsulant layer can be embossed in the inactiveregions so that the roofing substrate is visible. The encapsulant layercan be, for example, a fluoropolymer such as anethylene-tetrafluoroethylene copolymer (e.g., TEFZEL), and can be boundto rest of the device with a layer of poly(ethylene-co-vinyl acetate).The encapsulant layer can optionally extend into the headlap area. Suchdevices are described in more detail in U.S. Pat. Nos. 5,575,861 and5,437,735, each of which is hereby incorporated herein by reference inits entirety. In the devices described therein, for example, thedistance W_(T) can be about eight inches, as described above, and/or thedistance W_(s) can be about eighteen inches, as described above. Incertain such devices, no actual cut-out tabs are provided on the roofingsubstrate; rather the encapsulant was embossed between laterallyadjacent photovoltaic elements to simulate the appearance of tabs.Notably, according to the present invention, such devices can be formedwith roofing substrates having height “H” of about eighteen inches, asdescribed above. Moreover, according to the present invention, suchdevices can be formed with roofing substrates having exposure areaheight “E” of about eight inches, and/or photovoltaic elements havingheight “P” of about eight inches, as described above.

In certain embodiments, a cap layer is disposed on the flexible roofingsubstrate. For example, as shown in schematic top view and in schematiccross-sectional view in FIG. 19, a cap layer can be disposed on theflexible roofing substrate to cover areas of the granule-coated zone inwhich a photovoltaic element is not disposed. In the photovoltaicroofing element 1905 of FIG. 19, flexible roofing substrate 1910 has agranule-coated zone 1914 on its top surface 1912. Affixed in thegranule-coated zone (through adhesive layer 1942), but not covering itcompletely, are two photovoltaic elements 1960. Cap layer 1972 isdisposed on top surface 1912 of flexible roofing substrate 1910 to covercertain areas of the granule-coated zone 1914 in which a photovoltaicelement 1960 is not disposed. The cap layer can optionally cover allexposed area of the granule-coated zone. As shown in FIG. 19, a caplayer can also cover electrical connections (e.g., electricalconnections 1974 to electrical cable 1975), thereby protecting them fromthe elements. Notably, a cap layer can cover electrical connectionsand/or wiring systems even when it is not used to cover exposed areas ofa granule-coated zone. In other embodiments, a cap layer can seal theedges of a joint between the photovoltaic element(s) and the flexibleroofing substrate, whether or not the photovoltaic element(s) cover theentire granule-coated zone, and whether or not the cap layer covers theentire granule-coated zone. For example, as shown in FIG. 19, cap layer1972 seals the joint between the flexible roofing substrate 1910 and thephotovoltaic elements 1960. The cap layer can be provided in individualpieces (e.g., tape-shaped strips), or as a single piece. For example, incertain embodiments, the cap layer can be provided as a single piecewith cutout areas to expose the photovoltaically active areas of thephotovoltaic elements. The cap layer can be provided, for example, asroofing membrane (e.g., self-adhesive, such as that available fromCertainTeed Corporation), shingle material, or other materials, and canbe itself coated with roofing granules. The cap layer can alternativelybe provided as a roof coating. Such roof coatings are known in the art,and can also provide other attributes to the roof, such as reflectivityof solar radiation. Coatings can be formed, for example, from acrylic orfluorinated polymers, or latex-based materials. A cap layer can coverone or more photovoltaic roofing elements.

Another embodiment of a photovoltaic roofing element 2005 is shown intop schematic view in FIG. 20. A flexible roofing substrate 2010 hasfour tabs 2006, each having a granule-coated zone 2014, and a mechanicalattachment zone 2019. A shim 2020 at the top surface of the roofingsubstrate has cutouts at two of the tabs, such that the shim has nomaterial in the fastening zone adjacent two of the tabs. A photovoltaicmodule 2060 having an active area 2063 is adhered to the granule-coatedzones, and has inactive extensions 2064 that lie in the cutout areas ofthe shim. These extensions can provide a mechanical attachment area forthe photovoltaic element, and moreover can provide an alignment featurefor the installation of the photovoltaic element on the flexible roofingsubstrate. When installed, the cutout areas can be covered by anoverlying flexible roofing substrate, thereby protecting the mechanicalattachment of the photovoltaic element.

Photovoltaic roofing elements of the present invention can be fabricatedusing many techniques familiar to the skilled artisan. Roofingsubstrates can be made using a variety of techniques. For example, whenthe roofing substrate is an asphalt shingle or an asphalt non-wovenglass reinforced laminate, the person of skill in the art can usemethods described in U.S. Pat. Nos. 5,953,877; 6,237,288; 6,355,132;6,467,235; 6,523,316; 6,679,308; 6,715,252; 7,118,794; U.S. PatentApplication Publication 2006/0029775; and International PatentApplication Publication WO 2006/121433, each of which is herebyincorporated herein by reference in its entirety. Photovoltaic roofingelements can be fabricated in a continuous process and then cut intoindividual elements as is done in the fabrication of asphalt shingles.When a continuous process is used, it can be necessary to individuallyprepare any electrical cables running between elements, for example bycutting the cables between elements and adding connectors to the cutends.

In certain embodiments, the present invention may also be practicedusing techniques described in U.S. Patent Application Publication nos.2005/0072456 and 2004/0144043, and in U.S. Pat. No. 4,860,509, each ofwhich is hereby incorporated herein by reference in its entirety.

In another aspect of the invention, a photovoltaic roofing systemcomprises one or more photovoltaic roofing elements as described hereindisposed on a roof deck. The photovoltaic roofing elements can bedisposed with a certain amount of overlap to provide a waterproofcovering, as is conventional in the roofing arts. The photovoltaicroofing system can include a wiring system as described above, or asdescribed in U.S. Patent Application Publication no. 2008/0271774 A1,which is hereby incorporated herein by reference in its entirety. Thephotovoltaic elements of the photovoltaic roofing elements are desirablyconnected to an electrical system, either in series, in parallel, or inseries-parallel, as would be recognized by the skilled artisan.Electrical connections can be made using electrical connectors, such asthose available from Tyco International, and those described in U.S.Patent Application Publication no. 2010/0105238, which is herebyincorporated herein by reference in its entirety. There can be one ormore layers of material, such as underlayment, between the roof deck andthe photovoltaic roofing elements of the present invention. Thephotovoltaic roofing elements of the present invention can be installedon top of an existing roof; in such embodiments, there would be one ormore layers of standard (i.e., non-photovoltaic) roofing elements (e.g.,asphalt coated shingles or membrane roofing) between the roof deck andthe photovoltaic roofing elements of the present invention. Electricalconnections are desirably made using cables, connectors and methods thatmeet UNDERWRITERS LABORATORIES and NATIONAL ELECTRICAL CODE standards.Even when the photovoltaic roofing elements of the present invention arenot installed on top of preexisting roofing materials, the roof can alsoinclude one or more standard roofing elements, for example to provideweather protection at the edges of the roof, or in any hips, valleys,and ridges of the roof, or in areas not suitable for photovoltaic powergeneration.

Photovoltaic roofing elements based on shingles can be arrayed on a roofdeck in a variety of ways. For example, in the photovoltaic roofingsystem 2180 shown in top schematic view in FIG. 21, photovoltaic roofingelements 2105 are arrayed as laterally-offset courses of shingles. Eachflexible roofing substrate 2110 is a four-tab shingle, with agranule-coated zone 2114 (shown exposed on one shingle) on each tab.Photovoltaic elements 2160 are disposed in the granule-coated zones 2114and adhered with adhesive (not shown). In one example, a shingle similarto the Grand Manor® Shangle®, available from CertainTeed Corporation,has a shingle exposure height of 8 inches and an overall shingledimension of 18 inches by 36 inches, with four tabs in the exposurearea. An encapsulated T-cell photovoltaic element (Uni-Solar Ovonic)equipped with a pressure-sensitive adhesive is attached to each of thegranule-coated zones of each shingle. In other embodiments, for examplewhen the shingle has one or more granule-coated zones having a height ofabout eight inches, an exposure area having a height of about eightinches, or both, a photovoltaic element having a height of about eightinches can be attached to each of the granule-coated zones of eachshingle, or span the granule-coated zones of two or more of the tabs ofeach shingle.

In certain embodiments, in shingles similar to those described above,the granule-coated zone(s) spans the length of the exposed area of eachshingle. The shingles can be applied (e.g., in a typical fashion) by aroofing professional, who need not have any particular expertise withrespect to photovoltaic systems. One or more extended lengthphotovoltaic elements can then be disposed in the granule-coated zonesas described above, spanning the length of a plurality of shingles. Forexample, the Centennial Slate™ shingle or Hatteras® shingle exposureheight of 8 inches could be entirely covered by the photovoltaic element(i.e., with a photovoltaic element having a height of about eightinches). In the photovoltaic roofing system 2280 shown in FIG. 22, acourse of three shingles 2210 is arrayed on a roof deck. The shingleshave granule-coated zones 2214, which include alignment marks 2228 asdescribed above. The photovoltaic element 2260 is provided as a strip,in roll form, and has alignment marks 2268 on its bottom surface. As thephotovoltaic element is unrolled and disposed on the granule-coatedzones, the installer can align the alignment marks on the photovoltaicelement with those on the granule-coated zone to ensure properplacement. Of course, alignment marks or features could alternatively(or also) be provided on the releasable liner. In other embodiments,alignment marks or features could be at other locations on the shingle,within the granule-coated zone, and/or on the photovoltaic elementitself. In certain embodiments, the photovoltaic element can have linesor other decorative effects of a dimension that would correspond to theaesthetics of surrounding conventional shingles on the roof. While FIG.22 shows a single photovoltaic element extending along shingles arrayedin a single dimension, in other embodiments, a single photovoltaicelement can be disposed on shingles in a two-dimensional array (i.e.,both across the roof and up the roof).

In certain photovoltaic roofing systems of the invention, at least about70%, at least about 80%, or even at least about 90% of the totalgranule-coated zone area of the flexible roofing substrates is coveredby photovoltaic elements.

In certain embodiments, a protective conduit covers the wiringinterconnecting the photovoltaic elements, thereby protecting it fromthe elements, for example as shown in FIG. 23. In the photovoltaicroofing system 2380 shown in partial schematiccross-sectional/perspective view FIG. 23, the conduit 2378 is at thejunction of two adjacent roofing membranes 2210, and covers wiringsystem 2377 that interconnects photovoltaic elements 2360. In otherembodiments, the conduit can be disposed in the middle part of amembrane (e.g., between the connectorized ends of thehorizontally-arranged photovoltaic elements). Of course, a conduit canalso be used with a shingle-based photovoltaic roofing system. Theconduit can, for example, be similar in structure to a wire coveringproduct such as is commonly used for covering wires or cables on floorsin office environments. Of course, the conduit can take any of a numberof other forms, such as round or rectangular tube. A cap layer (e.g.,protective tape or cover sheet) comprising a suitable roof coveringmaterial can also be applied over a conduit so as to provide a desiredaesthetic effect or weathering protection to the conduit. A cap layercan also or alternatively be disposed within the conduit to providefurther protection.

In another embodiment, a protective covering is disposed over theelectrical connections. As shown in partial schematic cross-sectionalview in FIG. 24, the protective covering can have holes formed thereinnear the electrical connections of the photovoltaic elements, so thatwires for connection to an electrical system can pass through the holesto a wiring system for collection of the power generated by thephotovoltaic elements. In the photovoltaic roofing system 2480 of FIG.24, the protective cover 2478 covers cables 2476 that interconnectphotovoltaic elements 2460 (disposed on roofing membranes 2410) into awiring system. The holes can be sealed with an appropriate adhesive orsealant, such as a butyl, a mastic, or a neoprene adhesive. The wiringsystem can be provided in a conduit, which can be mounted within theroofing system and covered by a conventional roofing material strip ortape. Alternatively, the conduit can be mounted above the surface of theroof in the vicinity of the electrical connections of the photovoltaicelements. For example, a conduit could be provided as a tube of anydesired geometry) supported on legs which have pitch pockets filled withtar, adhesive, caulk, or the like to accommodate dimensional changes orvibrational effects experienced during use, this minimizing transfer offorces to the wiring system.

In other embodiments, individual photovoltaic elements are electricallyinterconnected in series, with sets of series-connected photovoltaicelements being connected to a wiring system or a bus system (e.g.,within a conduit) along one or more edges of a roof section.

Another aspect of the invention is a kit for the installation of aphotovoltaic roofing system, the kit comprising one or more flexibleroofing substrates as described above; and the adhesive as describedabove. In certain embodiments, the kit includes one or more photovoltaicelements suitable for disposition on the adhesive when the adhesive isdisposed in one or more of the granule-coated zones on the top surfaceof the flexible roofing substrate. In other embodiments, the kitincludes one or more photovoltaic elements having on their bottomsurfaces an adhesive suitable for adhering the photovoltaic elements tothe flexible roofing substrates. The one or more photovoltaic elementscan be selected to be compatible, both in size and in adhesivecharacteristics as described above, with the flexible roofingsubstrates. Accordingly, in certain embodiments, the one or morephotovoltaic elements have a height of about eight inches. The one ormore flexible roofing substrates can have, for example, one or moregranule-coated zones having a height of about eight inches; an exposurearea having a height of about eight inches; or both. In otherembodiments, the kit does not include photovoltaic elements. Such a kitcan be useful for the person of skill in the art, because it allows thephotovoltaic elements to be selected for the particular applicationdesired by the end user. The person of skill in the art can customizethe application of the adhesive to the flexible roofing substrates afterthe photovoltaic elements are selected.

Another aspect of the invention is a method for installing aphotovoltaic roofing system as described above on a roof deck. First, aflexible roofing substrate as described above is installed on the roofdeck. Then, on at least a portion of the granule-coated zones anadhesive suitable for securing a photovoltaic element to one or more ofthe granule-coated zones is disposed. Then, one or more photovoltaicelements are disposed on the adhesive on the one or more granule-coatedzones, thereby adhering the photovoltaic elements to the flexibleroofing substrate. When installing multiple flexible roofing substratesand/or photovoltaic elements, the person of skill in the art can performthe steps in any convenient order. For example, all (or a substantialnumber) of the flexible roofing substrates can be installed on the roofbefore any adhesive is applied. In fact, the flexible roofing substratescan remain on the roof for some time (e.g., at least an hour, at least aday, or even at least a week) before the adhesive is applied. Theflexible roofing substrates can be installed robustly in a rugged mannerto cover the roof; this step can be performed by a roofing professional,who need not have any particular expertise with respect to photovoltaicsystems. The adhesive can be applied to a plurality of granule-coatedzones before any photovoltaic elements are adhered thereto. For example,an installer can apply adhesive to a few rows of flexible roofingsubstrates at a time, then adhere photovoltaic elements to the appliedadhesive, before moving down the roof to the next few rows of flexibleroofing substrates. Of course, in other embodiments, the photovoltaicelement can be adhered to the adhesive immediately after it is appliedto the granule-coated zone.

Another aspect of the invention is a method for installing aphotovoltaic roofing system as described above on a roof deck. First, aflexible roofing substrate as described above is installed on the roofdeck. Then a photovoltaic element having an adhesive on its bottomsurface is provided. The adhesive of the photovoltaic element isdisposed on at least a portion of the granule-coated zones, therebyadhering the photovoltaic elements to the flexible roofing substrate. Incertain embodiments according to this aspect of the invention, aphotovoltaic element with a peel-and-stick adhesive on its bottomsurface can be adhered directly on a granule-coated zone of analready-installed flexible roofing substrate.

Another benefit derived in certain embodiments of the invention is thatwhen photovoltaic elements are separately installed on a roof, it ispossible to test the performance of the photovoltaic elements beforethey are installed on the roof. Such testing can be performed, forexample, immediately prior to attachment, so that any faultyphotovoltaic elements are discovered before they are attached to theflexible roofing substrate.

The flexible roofing elements can be applied to the roof deck inbottom-up manner (i.e., from the lower edge of the roof to the upperedge), as is conventional. The photovoltaic elements can then beinstalled, for example, from the top of roof to the bottom. Top-downinstallation of the photovoltaic elements can allow the more fragile andpotentially slippery photovoltaic elements to be applied in a moregentle manner, and without the need for an installer to walk onalready-installed photovoltaic elements. Moreover, top-down installationof the photovoltaic elements can allow the adhesion of the photovoltaicelements to the roofing substrates to build over time, without thepotential of being disturbed by an installer walking on or otherwisedisturbing them. Of course, the photovoltaic elements can be installedin any other convenient order.

Another aspect of the invention provides a method for installing aphotovoltaic roofing system on a roof deck that already has disposedthereon at least one flexible roofing substrate having a top surface,the top surface having one or more granule-coated zones thereon capableof acting as a receptor zone or an exposure zone, each zone beingadapted to receive one or more photovoltaic elements, as describedabove. The method includes disposing on at least a portion of thegranule-coated zones an adhesive suitable for securing a photovoltaicelement to one or more of the granule-coated zones. Then, one or morephotovoltaic elements are disposed on the adhesive on the one or moregranule-coated zones, thereby adhering the photovoltaic elements to theflexible roofing substrate. The method steps can be performed asdescribed above. This aspect of the invention allows the person of skillin the art to retrofit existing roofing elements with a photovoltaicsystem.

Another aspect of the invention provides a method for installing aphotovoltaic roofing system on a roof deck that already has disposedthereon at least one flexible roofing substrate having a top surface,the top surface having one or more granule-coated zones thereon capableof acting as a receptor zone or an exposure zone, each zone beingadapted to receive one or more photovoltaic elements, as describedabove. The method includes providing a photovoltaic element having anadhesive on its bottom surface; and disposing the adhesive on at least aportion of the granule-coated zones, thereby adhering the photovoltaicelements to the flexible roofing substrate. The method steps can beperformed as described above. This aspect of the invention allows theperson of skill in the art to retrofit existing roofing elements with aphotovoltaic system.

In other embodiments, the adhesive is applied to the flexible roofingsubstrate before the flexible roofing substrate is installed on theroof. For example, the adhesive can be disposed on the flexible roofingsubstrate at the worksite, but before installation. This can allow theindividual materials to be transported more efficiently, and be puttogether to fit the particular dimensions of the roof. In otherembodiments, the adhesive can be disposed on the flexible roofingsubstrate in a factory or workshop setting. In such embodiments, the useof a flexible roofing substrate with a granule-coated zone can increaseadhesion of the photovoltaic roofing element without sacrificingproperties of the rest of the flexible roofing substrate, and canincrease process flexibility during manufacture. For example, in someembodiments, the adhesive is applied only after the selection of aphotovoltaic element for use in the system is finalized. Accordingly,the person of skill can adapt stock flexible roofing elements andadhesives for use with any desired photovoltaic element.

A selection of sample drawings of various embodiments of the inventionis provided in FIGS. 25-28. FIG. 25 is a perspective view of a shinglehaving a base layer of shingle material, granule coated in its exposurearea, and a shim in the headlap zone of the shingle. As described above,the top face shim in the headlap region creates thickness to balance thedimensions of a photovoltaic element. FIG. 26 is a perspective view oftwo such shingles applied side by side (e.g., in a single course on aroof). The optional top face shim, as described above, allowsflexibility for use of slightly thicker photovoltaic elements whilestill providing a downward flow of water over the roof surface. FIG. 27is a perspective view of a photovoltaic element adhered in thegranule-coated zones of the shingles of FIG. 25 (along with a schematicdepiction of a photovoltaic element). The photovoltaic elements of FIG.27 include lines that match the periodicity of the tabs in the shinglesof FIG. 25. FIG. 28 shows a second course of shingles applied on a roofand equipped with photovoltaic elements as described above.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the scope of the invention. Thus, it is intendedthat the present invention cover the modifications and variations ofthis invention provided they come within the scope of the appendedclaims and their equivalents.

1-27. (canceled)
 28. A method for installing a photovoltaic element on aroofing product, the roofing product being disposed on a roof, theroofing product having a top surface and comprising a flexible roofingsubstrate having a top surface, the top surface having one or moregranule-coated zones thereon capable of acting as a receptor zone or anexposure zone, each granule-coated zone being adapted to receive one ormore photovoltaic elements, the method comprising disposing on at leasta portion of the one or more granule-coated zones of the roofing productan adhesive suitable for securing a photovoltaic element to one or moreof the granule-coated zones, the adhesive being capable of forming abond to the granules and the top surface of the flexible roofingsubstrate, the adhesive being disposed at the top surface of the roofingproduct; then disposing one or more photovoltaic elements on theadhesive disposed at the top surface of the roofing product in the oneor more granule-coated zones of the top surface of the flexible roofingsubstrate, thereby adhering the photovoltaic elements to the flexibleroofing substrate.
 29. The method according to claim 28, wherein theflexible roofing substrate is a bituminous substrate.
 30. The methodaccording to claim 28, wherein the flexible roofing substrate is abituminous roofing membrane.
 31. The method according to claim 28,wherein the flexible roofing substrate is an asphalt shingle.
 33. Themethod according claim 28, wherein the top surface of the flexibleroofing substrate in the granule-coated zone is recessed from the topsurface of the flexible roofing substrate in the area adjacent to thegranule-coated zone.
 34. The method according to claim 28, wherein thegranules in the granule-coated zone are embedded in the material of theroofing substrate more deeply than are the granules in the in theinactive zone.
 35. The method according to claim 28, wherein the topsurface of the flexible roofing substrate has solar reflectiveproperties.
 36. The method according to claim 28, wherein the surface ofthe one or more granule-coated zones or the top surface of the flexibleroofing substrate in the area adjacent the one or more granule-coatedzones includes one or more alignment marks.
 37. The method according toclaim 28, wherein at least some of the granule-coated zones remainexposed as exposure zones.
 38. The method according to claim 28, whereina mechanical fastener is used together with the adhesive in theattachment of the photovoltaic elements to the flexible roofingsubstrate.
 39. The method according to claim 38, wherein thephotovoltaic element includes a fastening zone or one or more fasteningtabs, which is fastened to the flexible roofing substrate by themechanical fastener.
 40. The method according to claim 28, wherein morethan one photovoltaic element is disposed on each granule-coated zone.41. The method according to claim 28, wherein one photovoltaic elementis disposed on more than one granule-coated zone.
 42. The methodaccording to claim 28, further comprising after disposing the adhesiveon the roofing product, disposing a releasable liner covering theadhesive; and before disposing the one or more photovoltaic elements onthe adhesive, removing the releasable liner from the adhesive.
 43. Themethod according to claim 28, wherein the granules of the one or moregranule-coated zones are different from the granules of the one or moreinactive zones.
 44. The method according to claim 28, wherein the topsurface of the flexible roofing substrate further comprises a headlapzone and one or more inactive zones adjacent the one or moregranule-coated zones and not covered when the photovoltaic roofingelement is installed.
 45. A method for installing a photovoltaic elementon a roofing product, the roofing product being disposed on a roof, theroofing product having a top surface and comprising a flexible roofingsubstrate having a top surface, the top surface having one or moregranule-coated zones thereon capable of acting as a receptor zone or anexposure zone, each granule-coated zone being adapted to receive one ormore photovoltaic elements, an adhesive suitable for securingphotovoltaic elements to one or more of the granule-coated zones, theadhesive capable of forming a bond to the granules and the top surfaceof the flexible roofing substrate and to the bottom surface of thephotovoltaic elements, the adhesive being disposed in the one or moregranule-coated zones, and a releasable liner covering the adhesive; themethod comprising removing the releasable liner from the adhesive; thendisposing one or more photovoltaic elements on the adhesive disposed atthe top surface of the roofing product in the one or more granule-coatedzones of the top surface of the flexible roofing substrate, therebyadhering the photovoltaic elements to the flexible roofing substrate.46. The method according to claim 45, wherein the flexible roofingsubstrate is a bituminous substrate.
 47. The method according to claim45, wherein the granules in the granule-coated zone are embedded in thematerial of the roofing substrate more deeply than are the granules inthe in the inactive zone.